1. The Field of the Invention
This invention relates to jacking apparatus for moving a load along a rail.
2. The Prior Art
Prior art jacking devices or apparatus for moving a heavy load along a rail have generally comprised cars or sleds with large hydraulic cylinders operatively connected to claws or dogs which successively engage holes or slots in a rail. The units have been strongly constructed but usually of massive, inflexible design, and with claws or dogs accurately placed to engage carefully machined and located rail holes or slots. Careful fabrication and placement of claws or dogs and holes or slots has been necessitated by the strong rigid, construction requiring accurate location of mating surfaces when these elements engage and disengage during repetitive, reciprocal movement of a hydraulic cylinder piston and resulting incremental movement imparted to the load. Large hydraulic cylinders and massive construction can provide adequate moving power, but lack flexibility for power distribution to a plurality of claws or dogs, if employed, for engagement with the rail holes or slots. Additionally, heavy and rigid mechanical connections between hydraulic cylinders and claws or dogs have resulted in less readily reversed mechanisms to provide movement of the load in the reverse direction, that is, for example, pulling instead of pushing.